That's been happening this week. I've been working on a large painting of a desert wash with smoke trees. Trying to make the smoke trees look right, and with the detail they need since they're somewhat close, has been enough to make me want to set the stinkin' thing aside and do something else.
BUT -- I'm getting to the end, and something inside me says "Don't quit on it now!" So I keep going, take frequent breaks, and figure I'll finish it by the end of the week.
The attached picture is the photo I'm working from, although I'm making some minor changes. The image shows a smoke tree-lined wash in Joshua Tree National Park just before sundown. And mind you -- I always work from my own photos along with reference material (drawings, color sketches, plein aire paintings, whatever).
Finally, don't forget -- my Website is http://www.southwestspaces.com.